Binary_checksum Craziness
Apr 17, 2007
Folks, hi.
Any idea why this patently different items return the same binary_checksum value:
select
binary_checksum('X', convert(datetime,'2006-13-12'), convert(datetime,'2007-17-04'), convert(datetime, null),'X','X','X','X','X','S','X') [1],
binary_checksum('X', convert(datetime, '2006-28-11'), convert(datetime,'2007-17-04'), convert(datetime, null),'X','X','X','X','X','B','X') [2]
The core of a very major system is based on these computing unique values for a unique set of expressions!
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Nov 20, 2007
Hi Experts,
Wt is the best way to identifying the changed record between staging table and the main table?
Currently im using BINARY_CHECKSUM and the article that shows the drawbacks of using it.
http://mgarner.wordpress.com/2007/10/31/not-using-checksum-or-binary_checksum-for-changing-dimensions/
Thanks in advance
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Jul 23, 2005
Hello,Do you know if the algorithm for the BINARY_CHECKSUM function in documentedsomewhere?I would like to use it to avoid returning some string fields from theserver.By returning only the checksum I could lookup the string in a hashtable andI think this could make the code more efficient on slow connections.Thanks in advanced and kind regards,Orly Junior
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Jul 23, 2005
Hi,It appears that binary_checksum can give the same checksum fordifferent strings, which is a bit worrying. (I guess the algorithm isthe problem in the context of a repeating pattern.)e.g.select binary_checksum('A'),binary_checksum('AAAAAAAAAAAAAAAAA'),binary_checksum('AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA A'),binary_checksum('AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAA')My question...Is this approach to generating checksums adequate for managing theobject scripts in the SQL Server to ensure that they haven't changed. Iguess that the probability of somebody making a change to a script andending up with the same checksum is almost negligible. Has anybody usedthis approach in an FDA validated production environment, i.e. 'no ifs,no buts'? Would it stand up to scrutiny?Any experiences, thoughts?RegardsLiam
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Jul 23, 2005
Gentlemen,I am using the following query to get a list of grouped checksum data.SELECT CAST(Field0_datetime AS INT),CHECKSUM_AGG(BINARY_CHECKSUM(Field1_bigint, Field2_datetime,Field3_datetime, Field4_bigint, Field5_bigint, CAST(Field6_floatDecimal(38,6)), Field7_datetime))FROM Table1WHERE Field0_datetime BETWEEN '2003-01-01' AND '2003-01-20'GROUP BY CAST(Field0_datetime AS INT)Please notice the used filter: from January 1 to January 20.That query takes about 6 minutes do return the data. The result is 18records.However, when I execute the same query filtering BETWEEN '2003-01-01' and'2003-01-10', this time it takes only 1 second to return data.When I execute the query filtering BETWEEN '2003-01-10' and '2003-01-20' thequery takes another 1 second to return data.So why 6 minutes to process them together??The table have an index by Field0_datetime.It contains about 1.5 millions records total, using around 1.7Gb ofdiskspace, indexes included.From 2003-01-01 and 2003-01-20, there are 11401 records selected. Don't looklike that much.The situation is repeatable, I mean, if I execute the queries back andagain, they takes the about the same ammount of time to execute, so I don'tthink this problem is related to cache or something like that.I would appreciate any advice about what might be wrong with my situation.Thanks a lot and kind regards,Orly JuniorIT Professional
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